Technodrive TMC40M clutch slipping?

[fishermantwo]

I had a similar problem with mine. When I bought the yacht, the gearbox had spent a lot of time underwater. It had the same symptoms. I found the correct info from the Twin Disc service notice and made the same adjustments with the Allen key and made sure the cable adjustments were correct. I noted Twin Disc said not to use Dexron 3 but 2 was OK. Can not buy Dexron 2 in Australia, so that's how I ended up with ISO 32. When I changed to ISO 32 it solved the slipping cone problem. However, I was still losing fluid and presumed the rear seal was gone. Removing the gearbox from a Beta 20 is a big job and I decided if I was going to all that effort, I would put on a new box. When I picked up the new box it was full with the correct amount of hydraulic oil. It was the same colour yellow as ISO32.

 

[oldmanofthehills]

No. It is a Twin Disc manufactured box, but it is a cone gearbox, just check the manufacturer's diagrams. Only use mineral base oil and stick to what the manufacturer says regarding the required oil. Beta are not the manufacturer. ISO32 is the closest you will get to with modern oils. INDUS PRO HYDRAULIC 32 | Penrite Oil

Thankyou for that, it is by no means clear from the literature supplied by BetaMarine or my conversations with them after failure.

If it is a cone clutch I am increasingly perturbed and unclear as to why it has such high catastrophic failure rates. The Yanmar GM10 engines cone clutch on my ex boat is still pretty good after nearly 45 years service

 

[doug748]

Thx that sounds like an idea but I think flush with the iso32, rotate the propshaft by hand at least 10-20 revolutions and empty, doing this twice will probably get rid of any dexron3, I think this may work as long as all the slippage has not worn away all the material, now I know why the oil went a dark colour after a short spin

Let us know if it improves things or not. I had no problems with my gearbox in 16 years and getting on for 2000 hours so it's all a bit rum.

 

[fishermantwo]

Thankyou for that, it is by no means clear from the literature supplied by BetaMarine or my conversations with them after failure.

If it is a cone clutch I am increasingly perturbed and unclear as to why it has such high catastrophic failure rates. The Yanmar GM10 engines cone clutch on my ex boat is still pretty good after nearly 45 years service

It's best to stick with the manufacturer's recommendations. The diagram shows the cones

 

[Boatbot]

Let us know if it improves things or not. I had no problems with my gearbox in 16 years and getting on for 2000 hours so it's all a bit rum.

Unfortunately after flushing and adding iso32 fluid it has not solved the slippage, clutch engages after reviing up gently it then grabs and the boat lurches fwd depending on the rpm so difficult getting out of berth etc, coming in to berth it will hold at slow speed but if you hit neutral then try to re engage it could be sketchy coming back to moor at the pontoon!!
We went out for the whole day motoring about 5miles and it held.
I think I will try to use it for the rest of the season, not sure whether to replace clutch and gearbox for £700 or re lap the clutch!!

 

[doug748]

At least the new gearbox is not expensive and, if you have had a recent quote, that price seems to have held for quite a few years, which is a surprise nowadays

A chum of mine replaced his gearbox and I'm pretty sure he rebuilt the old one must ask him.

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